This invention relates to attachments for a shotgun, and in particular to an attachment for use with the muzzle end of a shotgun barrel.
It is known to provide choke tubes as attachments for a shotgun barrel. In fact, many shotgun barrels have an internal thread formed in the barrel at the muzzle end, and a shoulder stop, so that a permanent or removable choke tube(s) may be threaded onto the barrel, through the use of a fine thread, such that the choke tube is threaded into the barrel until a first end of the choke tube engages and seats against the shoulder as described in U.S. Pat. No. 6,052,935. The choke tube may have an interior configuration to modify a pattern of the shot that are released from the shotgun shell when it is fired. This interior configuration may include a narrowing or a widening of the internal diameter interior of the choke tube, and may also include abrupt steps or pins that protrude into the inner passage of the choke tube to engage the wad of the shotgun shell. For example, U.S. Pat. No. 2,092,649 shows such a choke tube. It is also known to provide a semiannular rib in conjunction with a nozzle to cause wad retardation by imparting a spin to the wad as it progresses down the nozzle. U.S. Pat. No. 3,045,379 also discloses these features. It is also known to provide conventional chokes on a shotgun muzzle, which offer a constriction or a constriction followed by an expansion to adjust the spray pattern. These restrictions can also slow down a wad traveling down the barrel but they apply radial forces to the shot pellets, thereby distorting the resulting pattern. U.S. Pat. Nos. 5,452,535 and 6,128,846 disclose the use of projecting pins or rings to engage the shot wad, and also the use of other attachments to the choke tube to further condition the shot pattern. U.S. Pat. No. 5,317,825 discloses an attachment to a choke tube to reduce recoil.
The sole means of attachment of these internal choke tubes is the meshing of the fine thread of the interior of the barrel and the exterior of the choke tube. This provides only a single point of attachment and this attachment is secured only by snugging the seating of choke tube against the shoulder on the inside of the barrel. U.S. Pat. No. 6,052,935 attempts to overcome the problem associated with the required fine threads, that is, the need to rotate the choke relative to the barrel through a large number of turns by using discontinuous threads. However, this requires precise machining of both the internal portion of the shotgun barrel, i.e., the “bore” and the choke tube, and also requires precise rotational alignment between the two parts upon assembly.
This single point of attachment, in a cantilevered fashion, is subject to loosening due to vibrations occurring during the firing of the shotgun, from recoil, internal pressure and also the passage of the shot charge, wad and propelling gasses, if the choke tube is not continuously checked for tightness, a hazardous condition resulting from a loose tube could result. The tube can loosen from its proper position in the bore, by way of the backing-out of its threads or else by lateral vibration and movement. The resulting hazards may include the failure of the choke-tube-to-bore gas seal, the deformation of the dimensions of choke tube, the threads and the bore of the barrel, which can occur with catastrophic result. The instability of such cantilevered seating of the tube also negatively affects the pellet patterning efficiency and consistency of the shotgun choke tube even when properly seated.
U.S. Pat. No. 5,317,825 discloses an attachment for the exterior of a choke tube, however this attachment is to reduce recoil and it is not described in this patent to use the attachment to stabilize or prevent the loosening of the choke tube relative to the barrel.
It would therefore be an improvement in the art if there were provided a means for securing the attachment of the choke tube, or other attachment for a shotgun barrel that would minimize or prevent the unwanted loosening and lateral instability of the choke tube or attachment.
Further, since the choke tube or other attachment for the shotgun barrel must be made by utilizing the fine threads on the interior of the shotgun barrel, the attachment process is time consuming because the attachment requires many revolutions of the choke tube or attachment until the end of the choke tube or attachment seats against the shoulder. In some instances, particularly in law enforcement and military use, shotguns are used for different applications that require installing different attachments to the muzzle end of the barrel of the shotgun, where the weight-bearing strength and the overall stability of the tube within the bore and time for changing between different attachments may be at a premium.
It would therefore be an improvement in the art if there were provided a means for attaching various attachments, in a stable and secure manner to a shotgun barrel, and to be able to do so in a less time consuming manner than utilizing the fine threaded attachment arrangement provided on the interior of the shotgun barrel.